Mine is 5 almost 6 and she can't deal with the big blocky very minimal stuff of the Atari era either so I get that comment. She's cutting her teeth on a GBC and also a NES Classic Edition. Good enough visuals and audio along with a better variety of games and play control/story choices. She mostly sticks to a few on the NES but I think it's more of a learning thing than dislike as it's better to get good, then move into another. Gameboy is like that, she's on a Super Mario Land kick.
This is a solid device though if you're part of the era or have the tolerance for the quality you'd find out of a 2600. 7800 I'd imagine having used one slightly is far more approachable.